Fix: problems pointed out by Copilot

https://github.com/emilk/egui/pull/8083#pullrequestreview-4364725473

crates/eframe/src/web/text_agent.rs

@@ -105,19 +105,17 @@ impl TextAgent {
                         active_range_chars,
                     });
                     runner.input.raw.events.push(event);
-                    runner.needs_repaint.repaint_asap();
                 } else {
                     if text.is_empty() {
                         return;
                     }
 
-                    if !event.is_composing() {
+                    input.set_value("");
-                        input.set_value("");
+                    let event = egui::Event::Text(text);
-                        let event = egui::Event::Text(text);
+                    runner.input.raw.events.push(event);
-                        runner.input.raw.events.push(event);
-                        runner.needs_repaint.repaint_asap();
-                    }
                 }
+
+                runner.needs_repaint.repaint_asap();
             }
         };
 

crates/egui-winit/src/lib.rs

@@ -689,16 +689,25 @@ impl State {
             // See <https://github.com/rust-windowing/winit/issues/2498>
             winit::event::Ime::Enabled | winit::event::Ime::Disabled => {}
             winit::event::Ime::Preedit(text, active_range_bytes) => {
+                let active_range_chars = match active_range_bytes.clone() {
+                    Some((start_bytes, end_bytes)) => {
+                        let (Some(start_chars), Some(middle_chars)) = (
+                            text.get(..start_bytes).map(|s| s.chars().count()),
+                            text.get(start_bytes..end_bytes).map(|s| s.chars().count()),
+                        ) else {
+                            log::warn!("{ime:?} is ignored due to invalid range");
+                            return;
+                        };
+                        Some(start_chars..start_chars + middle_chars)
+                    }
+                    None => None,
+                };
+
                 self.egui_input
                     .events
                     .push(egui::Event::Ime(egui::ImeEvent::Preedit {
                         text: text.clone(),
-                        active_range_chars: active_range_bytes.map(|(start_bytes, end_bytes)| {
+                        active_range_chars,
-                            let start_char = text[..start_bytes].chars().count();
-                            let end_char =
-                                start_char + text[start_bytes..end_bytes].chars().count();
-                            start_char..end_char
-                        }),
                     }));
             }
             winit::event::Ime::Commit(text) => {

crates/egui/src/style.rs

@@ -1641,7 +1641,7 @@ impl ImeComposition {
             color: active_underline_stroke.color.linear_multiply(0.5),
         };
         Self {
-            active_underline_stroke: Stroke::new(2.0, Color32::from_rgb(192, 222, 255)),
+            active_underline_stroke,
             inactive_underline_stroke,
         }
     }

crates/egui/src/text_selection/visuals.rs

@@ -140,10 +140,27 @@ pub(crate) fn paint_ime_preedit_text_visuals(
     mut relative_active_range: Option<std::ops::Range<CCursor>>,
     time_since_last_interaction: f64,
 ) {
-    if preedit_range.is_empty() {
+    /// Instead of implementing [`PartialOrd`] and [`Ord`] for [`CCursor`] to
+    /// make [`std::ops::Range::is_empty`] available, we use this helper
+    /// function instead.
+    ///
+    /// These traits are intentionally not implemented because
+    /// [`CCursor::prefer_next_row`] makes it difficult to define a clear
+    /// ordering between two [`CCursor`]s.
+    fn is_cursor_range_empty(range: &std::ops::Range<CCursor>) -> bool {
+        range.start.index == range.end.index
+    }
+
+    if is_cursor_range_empty(&preedit_range) {
         return;
     }
 
+    if let Some(relative_active_range) = &mut relative_active_range
+        && relative_active_range.end.index > preedit_range.end.index - preedit_range.start.index
+    {
+        relative_active_range.end.index = preedit_range.end.index - preedit_range.start.index;
+    }
+
     if matches!(ui.ctx().os(), crate::os::OperatingSystem::Windows)
         && let Some(r) = &relative_active_range
         && r.start.index == 0
@@ -163,7 +180,7 @@ pub(crate) fn paint_ime_preedit_text_visuals(
     let inactive_underline_stroke = visuals.ime_composition.inactive_underline_stroke;
 
     if let Some(relative_active_range) = &relative_active_range
-        && !relative_active_range.is_empty()
+        && !is_cursor_range_empty(relative_active_range)
     {
         if relative_active_range.start.index > 0 {
             paint_underlines(
@@ -185,7 +202,9 @@ pub(crate) fn paint_ime_preedit_text_visuals(
             active_underline_stroke,
         );
 
-        if relative_active_range.end < preedit_range.end - preedit_range.start.index {
+        if !is_cursor_range_empty(
+            &(relative_active_range.end..(preedit_range.end - preedit_range.start.index)),
+        ) {
             paint_underlines(
                 pos,
                 painter,
@@ -207,7 +226,7 @@ pub(crate) fn paint_ime_preedit_text_visuals(
     }
 
     if let Some(relative_active_range) = relative_active_range
-        && relative_active_range.is_empty()
+        && is_cursor_range_empty(&relative_active_range)
     {
         let active_cursor = preedit_range.start + relative_active_range.start.index;
         let cursor_rect = cursor_rect(galley, &active_cursor, row_height);